Field of the Invention
The present invention relates to a matrix liquid crystal display element employing thin film transistors (hereinafter abbreviated to "TFTs") as address element and, more specifically as a matrix liquid crystal display elements employing inverse stagger TFTs using an amorphous silicon film as a semiconductor film as address elements.
Description of the Prior Art
FIGS. 3(a) and 3(b) illustrate the construction of an exemplary matrix liquid crystal display element employing inverse stagger TFTs as address elements. This liquid crystal display element is formed by forming gate electrodes 3, a gate insulating film 4, an amorphous silicon (hereinafter referred to as "a-Si") film 5, an insulating film 6, an n.sup.+ -type a-Si film 7, source and drain electrodes 8, picture element electrodes 9 for display and a protective film 10 one over another on an insulating substrate 1. The insulating substrate 1 is a glass plate, and the gate electrodes 3 are formed of tantalum (Ta). When the gate electrodes 3 are formed by a wet etching process using a tantalum etching solution, the glass insulating substrate 1 is eroded by the etching solution and thereby the surface of the glass insulating substrate 1 becomes cloudy and rough. Nevertheless, no structure for solving such a problem has been known. FIG. 4 illustrates another conventional liquid crystal display element which includes an insulating film 2 in addition to the above-noted elements illustrated in FIGS. 3(a) and 3(b).